Chloride transport across placental microvillous membranes measured by fluorescence

Journal Article · Thu Dec 01 00:00:00 EST 1988 · American Journal of Physiology; (USA)

OSTI ID:6227991

Illsley, N P; Glaubensklee, C; Davis, B; Verkman, A S ^[1]

---

1. Univ. of California, San Francisco (USA)

Chloride transport across human placental microvillous vesicle membrane was investigated using the fluorescent probe SPQ (6-methoxy-N(3-sulfopropyl)quinolinium). Chloride influx (J{sub Cl}) was calculated from the initial rate of quenching of intravesicular SPQ fluorescence by chloride. J{sub Cl} measured by SPQ fluorescence was not significantly different from J{sub Cl} measured by uptake of {sup 36}Cl; SPQ did not affect measurements of J{sub Cl}. J{sub Cl} was increased 51% by a 58-mV membrane potential. Voltage-stimulated J{sub Cl} showed a saturable dependence on chloride concentration with a dissociation constant (K{sub d}) of 18 {plus minus} 5 mM and was inhibited by diphenylamine-2-carboxylate with an apparent inhibitory constant of 0.13 {plus minus} 0.03 mM. The activation energy calculated for voltage-stimulated J{sub Cl} was 4.6 {plus minus} 0.6 kcal/mol. J{sub Cl} was also stimulated by a reduction in the external pH from 7.0 to 5.5 (internal pH = 70). pH-stimulated chloride influx was increased by trans-HCO{sub 3} and was inhibited by dihydro-4,4{prime}-diisothiocyano-2,2{prime}-disulfonic stilbene. Uptake of {sup 36}Cl into microvillous vesicles was stimulated by trans-Cl. pH-stimulated J{sub Cl} showed a saturable dependence on chloride with a K{sub d} of 38 {plus minus} 6 mM but was not affected by membrane potential. No evidence was found for Na- or K-coupled chloride cotransport. These findings demonstrate the presence of a saturable chloride conductance and an electroneutral chloride-bicarbonate exchanger in the placental microvillous membrane.

• OSTI ID: 6227991
• Journal Information: American Journal of Physiology; (USA), Vol. 255:6; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHLORINE 36
UPTAKE
MEMBRANE TRANSPORT
BIOCHEMICAL REACTION KINETICS
PLACENTA
PHYSIOLOGY
ACID CARBONATES
DOSE-RESPONSE RELATIONSHIPS
FLUORESCENCE
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
ALKALI METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHLORINE ISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
FETAL MEMBRANES
ISOTOPES
KINETICS
LIGHT NUCLEI
LUMINESCENCE
MEMBRANES
NUCLEI
ODD-ODD NUCLEI
RADIOISOTOPES
REACTION KINETICS
YEARS LIVING RADIOISOTOPES
551001* - Physiological Systems- Tracer Techniques